1. Field of the Invention
The invention relates to a method for monitoring for a rupture in (i.e., a breakthrough through) a storage element of a fuel tank system.
2. Related Art
Numerous measures have been introduced in recent decades for reducing the pollutant emissions of motor vehicles. One such measure consists in using a fuel tank system in which a fuel tank is connected to a storage element for the temporary storage of hydrocarbons. During the refueling of motor vehicles, hydrocarbons are outgassed from the fuel, wherein it is sought to prevent the hydrocarbons from passing into the atmosphere. Also, in the presence of high temperatures or when driving over uneven surfaces, increased outgassing of hydrocarbons from the fuel occurs, wherein it must be ensured, in an effective manner, that the hydrocarbons do not escape into the atmosphere. In particular, in the case of hybrid vehicles, in which the internal combustion engine is entirely shut down over long traveling distances, it is necessary for outgassed hydrocarbons to be temporarily stored in an effective manner in order to be burned at a later point in time upon a restart of the internal combustion engine. For this purpose, fuel tank systems have become established that are composed of a fuel tank and a storage element for the temporary storage of hydrocarbons, wherein the fuel tank and the storage element are connected to one another such that the hydrocarbons outgassed from a fuel situated in the fuel tank are stored in the storage element, wherein the storage element is connected to a first line through which fresh air can be delivered to the storage element, and the storage element is connected to a second line connecting the storage element to an intake line and through which fresh air enriched with hydrocarbons can be delivered from the storage element to the intake line. In this way, the storage element can be cyclically purged with fresh air, and the stored hydrocarbons can be supplied to an intake line connecting the internal combustion engine to the air filter and supplying air for combustion to the internal combustion engine. It is thus possible for the hydrocarbons outgassed from the fuel tank to be burned in the internal combustion engine, reliably preventing escape of the hydrocarbons into the atmosphere.
An example of a fuel tank system according to the prior art can be found in the PCT application with the file reference PCT/KR2011/006516. The storage element however has only a limited storage capacity for the hydrocarbons outgassed from the fuel, which is a problem in particular in the case of hybrid vehicles, because the internal combustion engine of a hybrid vehicle is at a standstill over long distances and periods of time. When the capacity limit of the storage element has been reached, there is the risk, in the event of a further follow-up flow of hydrocarbons from the fuel tank into the storage element, of a so-called breakthrough of the hydrocarbons through the storage element. In the event of a breakthrough of this type through the storage element, no further hydrocarbons can be captured by the storage element, and the hydrocarbons seek a path through the storage element into the surroundings of the tank system and thus into the atmosphere. Therefore, it is necessary over the entire service life of the motor vehicle to reliably identify a rupture in (i.e., breakthrough through) the storage element, in order for the rupture in the storage element to be prevented “on board”, that is to say during the operation of the motor vehicle, for example by virtue of a purging process of the storage element being initiated, wherein the outgassed hydrocarbons are depleted by being burned in the internal combustion engine.